1. Field of the Invention
The field of the invention relates to data processors and in particular to the storage of system configuration data on these data processors.
2. Description of the Prior Art
Processors need to store data that is to be processed and instructions for controlling the processing of this data. When using this information, the processor may store it in general purpose registers where it is easy and quick to access. With increasing parallelism of processors which may involve instructions executing out of order, it may be necessary to keep more than one copy of a data value and this is done by renaming the general purpose registers that store this data.
Processors also store information regarding the configuration of the processor. This data is data that the software uses to configure the hardware rather than internal program data. This data is stored in system configuration registers, which are registers that are generally not accessed often, but store data that is required for the system to operate correctly. The values held in system configuration registers configure the hardware and as such tend to be located close to the hardware component that they relate to. An example of such a register is the page table base register which is used on tablewalks. Another example is the configuration register which indicates if caches, MMU and other memory system features have been enabled. As noted above because of their usage model these registers tend to be located physically close to where they are used.
A drawback of this distributed model is that it can make architectural reads and writes of these register values slow to execute.